1. Field of the Invention
This invention relates to brake systems and, more particularly, to improvements in force and torque measuring apparatus for brakes and their use in brake systems; with particular reference to heavy truck brake systems in use in vehicles which are being driven.
2. Description of the Prior Art
In the prior art, it is known that brake systems, including individual brakes or brakes operating in combination with one another are subjected to variations in adjustment, wear and tear as well as to problems relating to the environment in which they are used. Thus braking forces become uneven and in some cases unpredictable. An example would be where oil leakage occurs and slicks up the surfaces in a particular brake on a particular wheel, causing it to react differently than the other brakes.
Also in the prior art, it was known to test brakes or to apply testing apparatus to the brakes for specific purposes. Such apparatuses were applied; then the test would be run; and then the apparatuses were removed; and then the brakes were put back on together with the wheels; and finally the truck was put back into service. For example, in U.S. Pat. No. 3,703,826, a gauge is clamped on and a measurement is taken. It is then removed and entirely replaced. Gauges were not, however, used as part of the operating running system on moving vehicles to collect and analyze data on a regular basis.
U.S. Pat. No. 5,215,154 shows a method and apparatus for determining the weight of the vehicle or the power output of its engine which comprises measuring either or both of acceleration and velocity of the vehicle, measuring the force causing the acceleration and velocity by measuring deformation or displacement of a drive train member, and then evaluating the weight of the vehicle from the measurements of acceleration and force and the engine power output from the measurements of velocity and force.
In the prior art of measuring, it is known to provide strain detecting load cells which are adapted to replace or be readily interchangeable with couplings such as pins or bolts. See, for example, the Kutsay U.S. Pat. Nos. 3,695,096 and 3,365,689.
Current braking systems used on most heavy trucks are reliable and effective systems. However, defects can occur as the components are worn through continued use, which can cause degraded brake performance and effectiveness.
Thus, a low-cost method to detect and measure the wheel-to-wheel and axle-to-axle differences in brake force/torque is desired.
Tests performed using experimental instrumented anchor pin models established that a clear correlation exists between the force sensing anchor pins and the actual torque produced at the brake FIG. 1.
In heavy truck brake systems the anchor pins and brake shoe rollers react to the load as the brakes are applied during brake stops of moving vehicles. Operational forces from the pressure of brake applications and the force generated from the torque due to brake drum/shoe friction are transferred to the brake anchor pins and rollers. These forces produce a stress on the anchor pins and rollers. By means of an internal strain gauged anchor pin, this shear stress can be instantaneously and continually measured by monitoring an electrical signal in response to the applied load. This signal can be used to evaluate brake performance and effectiveness, thereby alerting the driver of brake system malfunctions or potential problems.
In dealing with many other types of brake force/torque measuring techniques, determination of forces require excessive modifications or costly attachments carrying gauges or some other measurement device. In most cases these attachments are not for operational use and do not measure brake forces in dynamic over-the-road conditions. In addition, brake system spatial limitations and operational conditions have prevented successful application of conventional strain gauge equipment and other measuring equipment. Principal factors have included undue complication and costs, requirement for radical design changes in the tested apparatus to provide additional clearances and/or protection for gauges, difficulty of installation, practical impossibility of accurate calibration in the field, and lack of available means to detect the angle of an applied load as well as its magnitude.
In view of the above, an object of the present invention is to provide a force measuring device for use in moving vehicles, which is adapted to replace and be readily interchangeable with the existing anchor pins, such as those produced by Rockwell International Corporation, 3135 West Maple Road, Troy, Mich., numbers 1259-N-252 and 1259-N-274 currently used in most xe2x80x9cPxe2x80x9d and xe2x80x9cQxe2x80x9d style brake systems of heavy trucks.
A further object is to provide a brake monitoring system which utilizes force sensing anchor pins, of the above type, to detect brake system out of adjustment and misalignment.
A further object is to provide a brake monitoring system that utilizes force sensing anchor pins to detect brake system malfunctions and failures in moving vehicles.
A further object is to provide a brake monitoring system which utilizes force sensing anchor pins to detect the presence of foreign substances such as oil, grease, or gear lube.
A further object is to provide a force/torque measuring pin of the above type which is formed with measurement zones of reduced external diameters within the bearing surface area, whereby shear strains produced in the pin by forces applied to the bearing surface areas are concentrated in the measurement zones.
A further object is to provide a force/torque measuring pin of the above nature formed with a axial bore, and including a plurality of electrical strain gauges attached to the circumferential surface of the bore within the zones of shear concentration.
A further object is to provide a pivotal force transducer including a combination of internal strain gauges to detect simultaneously the mutually perpendicular radial components of the shear strain produced by components of a force angularity applied to the transducer during brake stops, whereby the magnitude of the total applied braking force, and the application angle of the forces may be ascertained.
Other objects and advantages of the invention will become more apparent from the following description and accompanying drawings forming part of the application.
We have invented a way of systematically making wheel to wheel force/torque comparisons for operating, that is, moving heavy trucks which are being driven in order to determine whether there is any degradation in brake system performance; thus, allowing for corrective action.
In particular we provide a force and torque measuring apparatus for use in heavy truck brake systems on vehicles which are being driven, comprising an anchor pin means as part of the load-bearing members, said anchor pin means having a plurality of force detecting load cells and measuring devices within said truck brakes; exterior measuring and monitoring instrumentation means; and connection means connected to said anchor pin means and said instrumentation means to permit measurement of the applied brake loads during operation of the vehicle as aforesaid, both as to magnitude and direction.
We also provide such an apparatus wherein the cells have working dimensions comprising short zones of decreased diameter so that strains are concentrated in these zones; and electrical strain gages are positioned within these zones connected to said connecting means to effect said measurements.
In accordance with our invention, we provide a method of sensing and correcting brake function in heavy truck brake systems in use in operating moving vehicles being driven over the road, comprising the steps of systematically making wheel to wheel force/torque comparisons in operating heavy trucks in order to determine whether there is any degradation in brake system performance; and then taking corrective action based on those comparisons.
For use in an operating vehicle having brakes as part of an operating brake system, we provide a force and torque measuring apparatus for use in said system, comprising: load bearing members; an anchor pin means as part of the load-bearing members; said anchor pin means having a plurality of force detecting load cells and measuring devices within said brakes; exterior measuring and monitoring instrumentation means; and connection means connected to said anchor pin means and said instrumentation means to permit measurement of the applied brake loads as to either magnitude or direction or both, during vehicle and brake system operation. The cells have working dimensions comprising short zones of decreased diameter so that strains are concentrated in these zones; and electrical strain gages are positioned within these zones connected to said connecting means to effect said measurements. The anchor pins are oriented with respect to a predetermined reference point in order to obtain the applied brake load direction.
The apparatus may further comprise incorporating an indication means in said vehicle and connected to said system to convey real-time system performance to the operator.
The apparatus may comprise using a processing means connected to said system to analyze and determine individual brake system performance and generate a warning when performance is reduced to a predetermined reference value.
For use in connection with an operating vehicle having wheels and brakes in a brake system, we have invented a method of sensing and correcting brake function in said system, comprising the steps of systematically making wheel to wheel force/torque comparisons during operation of said vehicle and brake system in order to determine whether there is any degradation in brake system performance; and then taking corrective action based on those comparisons. The method further comprises using a means of correction verification to verify manual brake adjustments through an additional processing correction adjustments. We provide a method of sensing and monitoring individual brake performance over time in operating heavy truck brake systems in order to determine any degradation in brake system performance; and then taking corrective action based on the performance history. This method may include a processing means to analyze and determine wheel to wheel force/torque comparisons and generate a warning when wheel to wheel differences become unbalanced to a predetermined reference value.
The thrust of applicant""s invention is to use the truck brake testing and monitoring system on a continuous in-service basis. To that end, the invention does not impact on the normal operation of the brake system; that is, it does not make a change in that system. In accordance with the applicants"" invention, brakes may be tested continuously during the normal in-service operation of a vehicle, because the existing anchor pin is replaced with their anchor pin. Thus, test results can be monitored continuously, just like a brake light which comes on when one steps on the brake pedal. Prior art systems relate only to separate brake tests on parked vehicles.
Brake performance is the overall ability to stop the vehicle in a desired amount of time. This means that in accordance with the present invention, the entire vehicle brake system is evaluated, instantaneously and simultaneously, not just one component or section at a time. The instrumented anchor pin of the present invention senses or measures the force on the anchor due to the reactive torque generated by the drums and brake pads during a braking event. This provides the ability to determine the actual torque developed at each wheel. This information is desired for several reasons:
a. To instantaneously perform wheel-to-wheel comparisons to establish balanced braking;
b. To provide real-time status of the braking performance (i.e., stopping ability), at each wheel, simultaneously; and
c. To provide the ability to identify brake malfunctions such as oil/grease on the pad linings, brake adjustments out of specification, or loss of air pressure, at each brake location, simultaneously.
xe2x80x9cOperationxe2x80x9d as that term is used to describe the present invention, is defined as normal, every day, over-the-road, in service operation. xe2x80x9cOperationxe2x80x9d does not mean activating the brakes in a controlled test environment. The invention does not make a change in the normal operation of the brake system and can be used as a permanent feature of the truck.
Further, the method of sensing and correcting the brake function is a method in that xe2x80x9coperatingxe2x80x9d system. It comprises making wheel to wheel force/torque comparison during xe2x80x9coperationxe2x80x9d of the vehicle.
The description of the invention relates to such an operating system.
Correction verification can be done at any time either during truck (vehicle) operation. The present invention will measure brake performance conditions on a continuous basis. The invention provides constant force monitoring and is not dependent on an attachable test device or remote test site.
The clamp-on system of the prior art, such as U.S. Pat. No. 3,703,826 to Burke can only be used at a test station, and is not applicable for every day performance monitoring. It only measures the spreading force of brake shoes. The device does not account for many other brake performance variables such as lining, alignment, or drum to shoe interface.
Vehicle brake system performance is evaluated instantaneously and simultaneously at all brake locations, not just one component or section at a time. Burke only measures the force to push brake pads apart. Burke does not account for different brake linings, wear, or other damage that might affect brake performance (brake torque/stopping power).